1. Field of the Invention
The present invention relates to a charging control apparatus for a vehicle for controlling the power generation of a generator to charge a battery for a vehicle and, more particularly, to a charging control apparatus which controls a rate of increase of a field current of the generator when an electric load was applied to the generator.
2. Description of the Related Background Art
Hitherto, there has been proposed a charging control apparatus shown in JP-A-62-64299, wherein a battery voltage and a predetermined voltage are compared and when the battery voltage is lower than the predetermined voltage, an up/down counter is incremented and, contrarily, when the battery voltage is higher than the predetermined voltage, the up/down counter is decremented.
In the above apparatus, by extending a period to increment the up/down counter, even if a battery voltage suddenly decreases by applying an electric load, the up/down counter is gradually increased, so that a field current is gradually increased as shown in FIG. 9. Therefore, the electric load is also slowly applied to an engine and an inconvenience such as an engine stall or the like can be prevented. However, the above conventional charging apparatus has a short coming as described below.
In the above apparatus, with a rectangular wave signal from the up/down counter and an output of a comparator for comparing the battery voltage with a reference voltage, an AND is calculated, whose respective wave forms are shown in (a}, (b) and (c) of FIG. 8. The field current is controlled according to the result of the AND, which includes non-exciting intervals where no field current is supplied.
When an electric load is suddenly applied to the battery, however, the battery voltage drops and a high (Hi) signal is outputted from the comparator as shown in (d) of FIG. 8. Consequently, the field current is controlled according to an AND signal having a wave form (e) of FIG. 8 which is identical to the wave form (a) of FIG. 8. Unlike the wave form (c) of FIG. 8, a lack of the non-exciting interval results in an increased exciting energy supplied to the field winding.
Therefore, as shown in FIG. 9, at a point where the electric load is applied, an ON dust factor of the pulsed field current is suddently increased by a certain amount upon a mean value of the duty factor which has been so far maintained, and the duty factor is gradually increased thereafter.
Thus, there may be adversary influences onto the engine of the sudden increase in the duty factor of the pulsed field current when an electric load is applied.